Vibrating heat exchangers are not new. In previous designs the material to be treated is conveyed by vibration on a pan or plate, which is provided with perforations to permit the passage of air from below the pan up through the material thereon to be collected in a hood above the material. The perforated pan or plate is designed to develop a high static resistance in the perforations, and in operation the material to be treated is agitated by vibration which, in combination with the resistance of the perforated plates, results in an action causing the air to pass around the particles developing what is known as a "fluidized bed."
The passage of air through the bed of material can be for cooling, heating, or other processing requirements. One of the more common applications of the vibrating heat exchangers of the prior art is in the cooling of foundry sand, in which case the air functions to evaporate the moisture content of the sand and simultaneously cools the material by the evaporative cooling effect.
It has been a requirement of the fluid bed cooling apparatus heretofore used that the material to be treated must be very well blended so that it is as homogenous as is possible. It has been common heretofore to pre-blend the material before introducing it to the fluid bed by treating the material in large rotating drums or mixers to blend the material and/or to uniformly distribute the moisture therein. Such pre-blending was a definite requirement of the previous apparatus, and maximum efficiency of the fluid bed cooler could be attained only with such pre-blended homogenized material.